Magnetron anode-cathode structure



March 6, 1956 w. CRAPUCHETTES 2,737,611

MAGNETRON ANODE-CATHODE STRUCTURE Filed Aug. 12, 1955 3 Sheets-Sheet l INVENTOR PAUL W. CRAPUCHETTES ATTORN EY March 6, 1956 P. w. C ZRAPUCHETTES 2,737,611

MAGNETRON ANODE-CATHODE STRUCTURE 5 Sheets-Sheet 2 Filed Aug. 12, 1953 INVENTOR PAUL M CRAPUCHETTES ATTO R N EY March 6, 1956 P. w. CRAPUCHETTES 2,737,611

MAGNETRON ANODE-CATHODE STRUCTURE Filed Aug. 12, 1953 3 Sheets-Sheet 3 INVENTOR PAUL w. CRAPUCHETTES BY ATTORNEY United States Patent" 2,737,611 I 'MAGNETRON ANODE-CATHODE STRUCTURE Paul W. 'Crapuchettes, Palo Alto, Calif., assignor to Litton Industries Inc., San Carlos, Calif., a corporation of Delaware Application August 12, 1953, Serial No. 373,7 2 13 Claims. (0]. 315-3953 This invention relates to magnetron tubes and more particularly to magnetron anode-cathode structures permitting precise positioning of the parts.

In magnetrons the proper spacing and positioning of the anode with respect to the cathode to assure the proper interaction space is very important. A radial displacement error of as little as will generally produce excessive "back heating and consequent loss of efliciency and other troubles. Particularly in making magnetrons to :operate in the upper frequency regions, ,where the dimensions are necessarily small it is difficult to control manufacturing tolerances so that the proper spacing is preserved.

It-is an object of this invention to providea magnetron structure wherein the anode-cathode spacing-may be adjusted after assembly, to obtain the desired operating characteristics. 1

:In accordance with this invention there is provideda relatively rigid anode resonator assembly positioned to surround the cathode, the anode assembly being mounted on a relatively flexible deformable body member, together with rigidly supported pressure bearing elements which may be adjusted to deform the body member to secure the desired centering of the electrodes.

he preferred structure the flexible body member is in the form of a cylinder within which the anode assembly is mounted. Longitudinal struts are rigidly supported onrings fastened to theends of the cylinder and in these struts are carried pressure control elements in the form. of screws which may exert pressureat different points about the body to control the centering :position of the anode. The rings may also serve to fasten one en'd'of bracing struts to prevent the output coupling unit from distorting the body member and thus displacing the anode.-

.The cathode may be centered with respect to the mag- 'of vanes 2 which ,form the anode resonator structure of the magnetron. This anode assembly is mounted within and fastened to a deformable body member 3 made thin enough to be relatively flexible. At the ends of cylindricalmember 3 are fastened two monel rings 4 and 5 which, together with the mounting .rings 6 and 7, provide rigid support for the ends of body member 3. Between rings 4 and 5 are longitudinally extending struts '8. Set screws 9 are mounted in each of. struts 8 and have their inner endsincontact with the outer surface of body member 3. Hence, by adjusting the setvscrews the member 3 may be distortedslightly altering the relative position of the anode assembly with respect to the centrally supported cathode assembly 10. To complete the magnetronstructure there may :be provideda pair of pole pieces 11 and 12, provided with aligned bore holes 13, 14 which serve to support the'cathode assembly 10. Pole piece 11 preferably is provided with a shoulder 15 against which the slidably positioned cathode assembly may be forced to abut. A pair of spring members 16, 17 are arranged in compression so as ,to tend to forcecathode assembly 10 against shoulder 15. By reason of the slidable mounting the cathode assembly may move longitudinally a suflicient distance ,to take .care of variation in heat expansion. However, spring members 16, -17 will at all times maintain this cathode against the shoulder 15. It will be noted that these spring members .are spaced sufficiently from the emitting areaof the cathode to remain relatively cool.

Thespring rnembers 16, 17 rest against bearing surfaces of metallic members 18,- 19 whichform part of the mag netron envelope but are insulated from one another and fromthe main body-portion of the magnetron so that they may serveas thecathode heating and control potential leads.

In anode ring 1 and body member 3 there are provided openingsZO, 21 which serve as=output coupling openings for extracting energy from the magnetron. An output coupler unit 22 in theform of a wave guide is secured to the flexible-body member 3 in communication with openings 20 and 21. I Fastened to a coupling ring 23 of output couplerZZ are a pair of supporting struts 24, 25. After the tube has been completed and adjustmentof the anode'centering-properly achieved struts 24 and 25 may be brazed or otherwisesecured to rings4 and 5. These 3 support struts will support the-weight of the output wave netron by bore holes provided in the polepieces. This cathode assembly preferably is slidable withinthe bore holes and is kept seated in proper longitudinal position by'means of pressure springs, which may also serve as electrical leads for the cathode. 1

The-above-mentioned and other features of this invention and the manner of attaining them will becomemore apparent'and the invention itself will be best understood byreference to the following description of. an embodiment of the invention taken in conjunctionwith the accompanying drawings, in which: i t I Figure 1 is a longitudinal sectional view of a magnetron incorporating the features of this invention;

Figure 2 is an end view of the anode assembly of Fig ure I viewed along the line 22 of Fig.- 1; and

' Figure 3 is an enlarged sectional view illustrating some details of the cathode assembly. i Turning now to the drawing, the general assembly of a magnetron in accordance with this invention is illustrated. The magnetron is providedwith a rigid anode assembly comprising a body portion 1 and a plurality guide from distorting member- 3 after adjustment has beenmade, thus preventing a misalignment or change in positioning of the anode with respect to the cathode.

For the sake of completeness-of illustration the usual output impedance ramp for the output coupler is shown at 26,and the usual'magnetron strapping rings are illustrated at 27,.2S. It will be understood that 'by using two set screws-9 ineach of the struts adjacent the ends of the magnetron anode assembly not only can the radial centering of the anode with respect to the cathode be readily achievedbut also.longitudinaldistortion maybe achieved so as to lock the element in the event the vanes are not quite parallel with the cathode.

In order to assure thecentering of the anode with respect tothe cathode, one convenient method of adjustment is anelectrical one. For, any given magnetic field and anode voltage, adjustment i'spmade until the magnetron current isat a minimum value. This will indicatethe optimumpositioning of the cathode-anode as sembly. Instead of adjustingfor such current minimum the output spectrum. of the magnetron may be. appliedto a cathode ray oscilloscope. The, adjustment may then be carried out until the most impro'ved spectrum of this output energy is observed. It .willalso be clear that any time after the tube has been completely constructed tests may be made and the proper adjustments for the most desirable characteristics of operation may be achieved.

Turning now to Fig. 3, a more detailed illustration of the cathode as shown in Fig. l is illustrated. The cathode assembly may comprise a heater filament 29 mounted within an emissive cathode shell 30, one end of the filament 29 being connected to the shell for the current returned path. The other end of filament 29 is connected to an output lead 31 while the other end of shell 30 may be brought out to a flange 32, which may serve as a spring bearing. Heat shields 33, 34 may be arranged at opposite ends of the filament 20 to reduce heat and electron losses for the inactive portions of the cathode proper. An insulating sleeve 35 is-arranged on one end of shell 30. This abuts against the edge of heat shield 33 and is adjusted in length so as to seat the entire assembly properly against shoulder when the assembly is in place. Another insulating sleeve 36 extends from the edge of heat shield 34 to the inner edge of flange 32 so as to carry the pressure exerted by spring 17 against flange 32 along the greater portion of shell 30. Since shell 30 is relatively thin it is preferable that only a small portion thereof necessary to furnish the emitting surface for the magnetron be permitted to carry the longitudinal pressure necessary for maintaining the assembly seated properly. An insulating cylinder 37 is arranged around lead conductor 31 to prevent short circuiting of this lead against shell 11 throughout most of its length. Near one end of lead 31 is fastened a pressure bearing head 38. The spring member 16 is shaped so as to bear against the edge of this bead 38 so as to serve as an output lead for the filament. Simultaneously the pressure exerted by spring 16 may be also carried to the cathode assembly, by means of an insulating sleeve 39 positioned between bead 38 and a surface. of flange 32.

It will be seen that this cathode assembly provides for a precise positioning of the cathode in the magnetrons as well as for the necessary current leads for the cathode. Thus, the cathode is rigidly held in position and adjustment of the spacing between the anode and cathode may be readily achieved simply by the anode adjustment arrangement specifically described above.

While the invention has been described in connection with a particular tube for the purpose of illustrating a preferred form of the invention, it will be readily understood that the principles of this invention are applicable to a wide variety of different constructions.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description ismade only by way of example and not as a limitation to the scope of my invention, as set forth in the accompanying claims.

What is claimed is:

1. A magnetron comprising a relatively rigid annular anode assembly, a cathode. rigidly mounted within said assembly and spaced therefrom, said magnetron having means for adjusting the anode cathode spacing, comprising a deformable support for said anode assembly fastened to opposite ends thereof and means mounted independently of said support and relatively rigid for adjustably controlling deformation of said support.

2. A magnetron assembly comprising a multiple resonator assembly of a relatively rigid substantially cylindrical body and a plurality of radially extending vanes within said body said magnetron assembly having a relatively flexible supporting cylinder to which said resonator assembly is fastened, a rigid support ring around said flexible support spaced from the'end of said resonator assembly, a plurality of rigid struts secured to said support ring at circumferentially spaced points about said supporting cylinder and substantially parallel thereto, and adjustable centering elements in said struts adapted to be moved into pressure contact with said supporting cylinder adjacent said assembly to flex said cylinder 4 transversely of the axis for adjustably positioning said resonator assembly.

3. A magnetron assembly according to claim 2, further comprising an energy output coupler mounted on the outer surface of said flexible member, and a bracing strut fastened to said support ring and to said output coupler.

4. A magnetron assembly according to claim 3, wherein two support rings are provided spaced from opposite ends of said anode assembly, and coupler support struts are fastened to each of said support rings.

5. A magnetron assembly according to claim 2, further comprising pole pieces provided with central bore openings mounted at the ends of said support cylinders, a cathode assembly slidably fitted into said bore openings and held in central position thereby with respect to the vanes of said resonators, and compression spring means bearing against one end of said cathode assembly to retain it in longitudinal position during operation, and to serve as an output lead for said cathode.

6. A magnetron assembly according to claim 5, wherein said cathode assembly comprises, a heater filament, an emissive sleeve surrounding said filament and connected at one end to said sleeve, and relatively rigid output leads connected to the respective other ends of said filament and said sleeve, said compression spring means bearing against said output leads.

7. A magnetron assembly according to claim 6, further comprising separate conductive envelope members sealed to said supporting cylinder in insulated relation to each other and to said cylinder, and wherein said compression'spring means comprises separate coil springs mounted between respective envelope members and said rigid conductors.

8. A magnetron comprising a relatively flexible cylindrical -body member, a cathode electrode fixedly mounted substantially centrally of said cylindrical body member, an anode, resonator assembly mounted on said member intermediate the ends and internally thereof, and surrounding said cathode electrode, a plurality of relatively rigid struts mounted externally of said member in fixed radial relation with respect to said cathode, longitudinally of said body member and circumferentially spaced therearound, and adjustable pressure producing elements in each of said struts for contacting said body member in the vicinity of said anode, whereby adjustment of said pressure-producing elements will serve to adjust the position of said anode with respect to said cathode.

9. A magnetron according to claim 8, further comprising a pair of rigid rings fixed to said bodymember at opposite ends thereof, said struts being fixed to bridge between said rings.

' l0.-A magnetron according to claim 9, wherein an output coupling opening is provided in said body member, further. comprising an output wave guide section mounted on said member in communication withsaid opening, and supporting struts fixed to said rings and to said wave guide section.

a ll. A;magnetron according to claim 8, further comprising pole pieces mounted at the ends of said body member on opposite sides of said anode, said pole pieces being provided with aligned central bore openings, said cathode electrode being mounted within the bore openings of said pole pieces.

12. A magnetron cathode mounting structure comprising two' spaced pole pieces provided with aligned bore openings, a cathode assembly slidably fitted into said bore openings and held in fixed radial position thereby, a stop shoulder in one of said pole piece openings to provide a longitudinal stop for said cathode assernbly at one end thereof, and compression spring means against the othe'rend of said cathode assembly serving to retain said assembly against said stop shoulder, and as an output lead for the cathode.

5 13. A cathode mounting structure according to claim 12, further comprising separate insulated conductive envelope members provided with bearing surfaces, said cathode assembly comprising a central filament lead provided with a bearing lead, and an outer conductor 5 lead provided with a bearing flange said spring means comprising a first coil spring between said bearing bead and the bearing surface of one of said envelope members, and a second coil spring between said flange and the bearing surface of another of said envelope members.

References Cited in the file of this patent UNITED STATES PATENTS 2,418,469 Hagstrum Apr. 8, 1947 2,478,644 Spencer Aug. 9, 1949 2,495,258 Iatesta Jan. 24, 1950 

